ALD is a known method for the deposition of thin films. It is a self-limiting, sequential unique film growth technique based on surface reactions that can provide atomic layer control and deposit conformal thin films of materials provided by precursors onto substrates of varying compositions. In ALD, the precursors are separated during the reaction. The first precursor is passed over the substrate producing a monolayer on the substrate. Any excess unreacted precursor is pumped out of the reaction chamber. A second precursor is then passed over the substrate and reacts with the first precursor, forming a monolayer of film on the substrate surface. This cycle is repeated to create a film of desired thickness.
ALD processes have applications in nanotechnology and fabrication of semiconductor devices such as capacitor electrodes, gate electrodes, adhesive diffusion barriers and integrated circuits. Further, dielectric thin films having high dielectric constants (permittivities) are necessary in many sub-areas of microelectronics and optelectronics. The continual decrease in the size of microelectronics components has increased the need for the use of such dielectric films.
Green, J., et al. report the synthesis and isolation of the Mo complex, Mo(C5H5)(NMe2)3. J. Chem. Soc., Dalton Trans., 1997, Pages 3219-3224.
U.S. Pat. No. 5,064,686 reports a Mo (IV) complex for use in chemical vapor deposition (CVD). Mo[N(Me)(Me)]4 was attempted in CVD. However, issues with thermal stability were noted in CVD and it has been found that although this precursor is similar in structure, it is not suitable for depositing a MoO2 layer.
Further, it was found that Mo(NtBu)2(NMe2)2 did not work well for forming MoO2 films by ALD because it formed MoO3 films which is unsuitable for DRAM. Therefore a need exists to discover new Mo precursors which are capable of depositing MoO2 films by ALD, which have improved thermal stability, higher volatility or increased deposition rates.